1. Technical Field
The present invention relates to a technique that enables scrolling of display contents of a display unit and, in particular, to a scrolling apparatus, a scrolling method, a scrolling program, and an integrated circuit which enable high-speed scrolling using a pointing device such as a touch panel.
2. Background Art
An exemplary conventional scrolling apparatus is provided with a memory buffer capable of storing display data in a greater range than a display range of a display unit, and increases processing speed during scrolling by loading, in advance, display data existing in a scrollable direction prior to performing a scroll operation to the memory buffer (for example, refer to Patent Document 1). FIGS. 12A to 12C are diagrams showing an example of display data loaded to a memory buffer according to Patent Document 1 described above. Prior to initial display, first, when a display range 500 is specified as an initial display area, display data arranged in the display range 500 shown in FIG. 12A is saved in a memory buffer. Subsequently, display data included in the display range 500 is displayed on a display unit to perform initial display. Next, as a prior loading process of a scroll operation, for example, if there is a possibility of scrolling being respectively performed by a maximum of one screen in upward, downward, leftward, and rightward directions, display data that is arranged in an area 501 which is an area created by expanding the display range 500 by a maximum of one screen in upward, downward, leftward, and rightward directions is stored in the memory buffer.
Next, when scrolling display, a scrolling direction is determined according to a movement position during a slide operation performed by a user. FIG. 12B shows contents of the memory buffer when scrolling is performed by one screen in the rightward direction. When scrolling toward the right, according to a movement position during a slide operation, a range displayed on the display unit is moved from the display range 500 in FIG. 12A to the display range 500 in FIG. 12B, and display contents are scrolled by continuously displaying display data included in the display range on the display unit. Finally, when the display range 500 is modified, display data corresponding to an area 502 (FIG. 12C) not yet stored in the memory buffer among areas having a possibility of being displayed on the display unit when scrolling is performed once again is stored in the memory buffer according to the modified display range 500.
By storing, before a scroll operation is performed by the user, display data having a possibility of being displayed on the display unit due to scrolling in the memory buffer in the sequence described above, processes of reading and loading display data to the memory buffer after a scroll operation is performed by the user and before a screen after scrolling is displayed on the display unit is eliminated to achieve high-speed scrolling.
However, with the conventional configuration described above, since display data in all areas having a possibility of being displayed due to a scroll operation by the user is loaded in advance, a significant amount of display data is loaded. Consequently, there is a problem of increased load processing time of display data and increased memory consumption for storing loaded display data.    Patent Document 1: Japanese Patent Application Laid-open No. 2000-47658